In a conventional door catch as shown in FIGS. 1 and 2, there is included a back plate 1 having two laterally symmetric sleeves 11 formed on a front face thereof. A steel ball 2 and a spring 3 are sequentially mounted in each of the two sleeves 11, and a screw 4 is screwed to a rear end of the sleeve 11 to confine the ball 2 and the spring 3 in the sleeve 11, so that the ball 2 is normally pushed by the spring 3 to partially project from a front open end of the sleeve 11. To use the door catch, first fixedly mount the back plate 1 on a wall 10 with fastening elements to correspond to a stop post 6 fixedly mounted on a back of a movable door leaf 20, so that the stop post 6 is clamped by and between the two steel balls 2 partially projected from the front ends of the two sleeves 11 when the door leaf 20 is turned toward the wall 10. The use of the screw 4 to confine the steel ball 2 and the spring 3 in the sleeve 11 is labor and time consuming, and it is possible the screw 4 becomes loosened to finally separate from the sleeve 11. Moreover, the conventional door catch with the above structure must be made of a metal material, and therefore requires a relatively high manufacturing cost.